"Correlation" designates a statistical measure which assess the extent to which two variables vary in the same direction or the extent and direction in which they diverge. A correlation of 1 means that the two variables move exactly together to the same extent and in the same direction. A correlation superior to 1 means that they move in the same direction, but that the movements affecting one are amplified. A correlation of -1 means that the two variables move in the same proportion, but in exactly two opposite directions.

(See Chapter 18 Risk and return of the Vernimmen)

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